A pivot pin which is provided with conical bushings arranged to take up play between the pivot pin and the elements that it connects, for example as described by NO302053, requires special tools when the pivot pin is to be fitted or removed, as the conical bushings have to be pushed in over or pulled off the pivot pin with great force for the articulation to be centred or the pivot pin to be released. An example of such a tool is described in NO328050. Pivot pins like that are often of very large dimensions; for example, it is not unknown to have a pin diameter of 500 mm and a pin length of 2000 mm. Having to provide such special tools for maintenance is a disadvantage, especially since a pivot pin of this kind often has to be repaired where the machine or implement that it is fitted to is being used.
The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.
The object is achieved through the features, which are specified in the description below and in the claims that follow.
For a pivot pin including at least a pin shaft with one conical end portion for receiving a conical, radially expandable bushing arranged to be tensioned against a bore in a first articulation element, an end plate is arranged, which is arranged to rest against an outward end face of the conical bushing and subject the bushing to an axial, inward push force when at least one first screw that is arranged in a cut-out in the end plate and is engaged in a threaded, corresponding bore in an end portion of the pin shaft is being tightened. Said first screw and bore are formed with a first thread diameter. Said screw hole and bore are preferably arranged at a distance from a centre axis through the pivot pin.
At least one threaded screw hole with a second thread diameter is arranged in the end plate and is arranged to receive a second screw. Said threaded screw hole is preferably arranged at a distance from a centre axis through the pivot pin.
The threaded screw hole in the end plate is preferably arranged to receive the second screw and is then formed with a thread diameter identical to said second thread diameter, which is larger than said first thread diameter. Several screw holes are preferably arranged on a pitch circle with an inter-centre distance larger than twice the second thread diameter.
A releasable coupling element connects the end plate and the bushing in such a way that an axial outward displacement of the end plate results in the bushing being pulled away from its engagement in the bore in the first articulation element. The coupling element is preferably provided as a coupling ring which is arranged to enclose the periphery of the end plate and to rest with inward-projecting edge portions against one or more faces facing away from the outward end face of the conical bushing, for example by engaging with a groove on an external periphery of the bushing or by grip-ping around an outward-projecting flange on the bushing, and to rest against a portion of an outward end face of the end plate. The coupling element is preferably provided with at least one lockable split for the coupling element to be easily removed from its engagement with the end plate and the bushing.
By screwing the second screw into the threaded screw hole of the end plate and into abutment against the end face of the pin shaft, the end plate may be moved away from the pin shaft, and the coupling element, which holds the end plate and bushing together, ensures that the bushing is pulled loose from the pin shaft and the bore of the first articulation element. In an embodiment in which the first and second screws are placed in the same screw hole in the end plate, it is an advantage if the end plate, before the second screw is screwed in, is rotated so that the second screw will not touch the threaded bore in the end portion of the pin shaft.
In a preferred embodiment, when receiving the first screw, the threaded screw hole is provided with a screw-hole bushing. The screw-hole bushing is provided with external threads arranged to engage with the threads in the screw hole. In a preferred embodiment, said threads and also the threads of the second screw are turned in the opposite direction to those of the first screw. A centre bore of the screw-hole bushing has a dimension that allows the threaded portion of the first screw to be passed through the bushing.
By providing the screw-hole bushing with a collar and outward-projecting lips which may be bent up into abutment against side faces of the screw head of the first screw, the first screw may be locked in a very effective way, as any tendencies of the first screw to unscrew itself, will immediately be prevented by such a rotary motion resulting in the screw-hole bushing screwing itself inwards in the threaded screw hole.